THE CRITERIA OF LIVINGNESS 103 



istics of living creatures. Hence this inquiry into the criteria 

 of livingness. The bearing of this on modern Xatural The- 

 ology is that an easy-going concept of ' organism ' is a dead 

 fly that may spoil many an ointment. 



SU3IMARY. 



If we are to reach a coherent view of Nature, such as could be 

 included in a philosophy, we must arrive at some definition of the 

 characteristics which mark off hving organisms from their not-living 

 surroundings. In the present state of science this definition cannot 

 be more than tentative, but it must be continually attempted. 



Living may be described as a twofold relation of action and re- 

 action between organisms and their environment, and living crea- 

 tures are always active towards two main results, self-maintenance 

 and the continuance of their race. But the difiScult question is: 

 What are the insignia of living creatures? 



The first is the power of persisting in a complex specific metabo- 

 lism, and in a corresponding specific organisation, (a) The essential 

 metabolism of life has to do with the up-building and down-break- 

 ing of protein substances in a colloid state, (b) Each living 

 creature has its own chemical individuality and its own specific 

 microscopic and ultra-microscopic architecture, (c) Part of the 

 secret of life is a correlation of chemical processes so that m 

 spite of ceaseless change the organism persists in its integrity 

 for days or years or centuries. It is always burning away; but 

 it is not consumed. 



Secondly there are the capacities of (a) growth, of (b) re- 

 production, and of (c) development — a triad of qualities. (a) 

 Organic growth, an increase in the amount of organised linng- 

 matter, is at the expense of materials different from those which 

 compose »the growing substance; it implies active assimilation 

 rather than passive accretion; it is very definitely a regulated 

 process. (b) The power of spontaneous division — leading on, 

 directly or indirectly, to the origin of new individualities — is 

 one of the momentous distinctions between the living and the 

 not-living, (c) Development is the actualisation of the intrinsic 

 manifoldness of the liberated fragment, sample, or cell, and may 

 be brought into line with the process of repairing the specific 

 organisation. 



